Judith Landa, a former investor in the Emerald South and Emerald North nursing homes, is suing County Executive Mark Poloncarz for slander and libel.
Since last year, Poloncarz has railed against the ownership of the two area nursing homes, where patients have suffered harm or died, and has been an outspoken critic of Landa and her husband, Benjamin.
He later said he would "never be silenced by threats of others" when it came to protecting residents' safety.
But he declined to comment Friday after Landa filed suit in State Supreme Court alleging Poloncarz uttered and tweeted "false statements," used her businesses for political gain, caused her business dealings to suffer financially and damaged her reputation.